Degradation and metabolism of imazapyr in soils under aerobic and anaerobic conditions

Abstract

The degradation of imazapyr in four soils was investigated under laboratory aerobic and anaerobic conditions. Under aerobic conditions, imazapyr degraded faster in yellow–red soil than in other soils, and its persistence decreased depending on soil pH in the order coastal soil (pH 8.8) > silt-loamy paddy soil (pH 7.9) > fluvio-marine yellow loamy soil (pH 7.1) > Yellow–red soil (pH 5.3). However, soil pH did not affect imazapyr degradation under anaerobic conditions. The half-lives of imazapyr in soils under aerobic conditions were in the range of 26–44 days estimated by the first-order kinetics model, while 3–10 days calculated by two-stage model under anaerobic conditions. The preceding results demonstrated that anaerobic conditions contributed to imazapyr disappearance in soils. Based on the spectral data of APCI-MS, ¹H NMR and IR, structures of the following metabolites: 2,3-pyridinedicarboxamide, 2,3-pyridinedicarboxylic anhydride and 2,3-pyridinedicarboximide for aerobic treatments; 2,3-pyridinedicarboxylic anhydride and 2-(4-hydroxy-5-oxo-2-imdazolin-2-yl) nicotinic acid for anaerobic treatments, were identified. Degradation mechanism under the different conditions was also discussed.

Keywords:

• Imazapyr
• Soils
• Aerobic conditions
• Anaerobic conditions
• Metabolites

Acknowledgements

The project was financially supported by Shanghai Branch, BASF (China) Co., Ltd. The authors are grateful to professor Sufen Han and Zhengmin Han of Nanjing Forestry University, and professor Yunlong Yu of Zhejiang University for their technical assistance.